At two installations (Forts Riley and McCoy), military training exercises or the risk of unexploded ordinance prevented us from searching the entire 2015 study area. Our results provide the most comprehensive assessment to date of the annual cycle and migratory behavior of Grasshopper Sparrows and Eastern Meadowlarks. We also report the distances (km) between individuals from the same population during the nonbreeding period (Finch et al., 2017), an MC estimate combining all populations, and the MC estimate for only the Midwest populations. We verified a good harness fit by ensuring that ~2 mm of vertical play occurred when we gently lifted the geolocator from a bird's back, or else we replaced the harness. The resulting estimates of migration routes, flight speed, and timing of migration were indistinguishable from our preliminary analyses. Eastern Meadowlark populations may be largely sedentary across much of their range, but available band recoveries (e.g., between Ontario, Canada to South Carolina, and between Indiana and Georgia, US) suggest that some individuals within northern populations are migratory (Jaster et al., 2003). by Mike Lanzone Migratory bird species with relatively restricted winter ranges are more likely to experience declines than species with broad nonbreeding ranges, which suggests that species with strong migratory connectivity are more susceptible to the effects of local nonbreeding habitat loss and degradation (Fuller, 2016; Gilroy, Gill, Butchart, Jones, & Franco, 2014; Sutherland, 1996). Similarly, analysis of satellite tracking data of Golden Eagles (Aquila chrysaetos) revealed that substantial illegal persecution (~one third of tagged eagles) in specific areas of the Highlands was responsible for declining populations in Scotland (Whitfield & Fielding, 2017). Sparrows were largely stationary at the nonbreeding grounds, spending only about a week (7.08 days ± 24.53, 0.00–87.67 days, n = 12) on the move. Of the remaining six tags, one malfunctioned soon after deployment and provided no useable data. Partial migration is a widespread characteristic of animal migration, in which populations consist of resident and migratory individuals (Lack, 2012); it has been documented in species such as Blue Tits (Cyanistes caeruleus), Northern Flickers (Colaptes auratus), and American Robins (Brown & Miller, 2016; Gow & Wiebe, 2008; Smith & Nilsson, 1987). The Migratory Bird Program is responsible for maintaining healthy migratory bird populations for the benefit of the American people. Similarly, Wood Thrush (Hylocichla mustelina) fall migration timing (e.g., departure date and duration) is highly variable across years (Stanley, MacPherson, Fraser, McKinnon, & Stutchbury, 2012). For Grasshopper Sparrow, its relatively short daily fall migration flights and its ability to rapidly discover newly‐created small pockets of habitat (Andrews, Brawn, & Ward, 2015; Hill & Diefenbach, 2014), suggest that the species may benefit from many scattered parcels of habitat throughout its migration corridor, as opposed to a few isolated reserves of large grasslands. (2013), we combined stopover events during migration that were <45 km apart due to the spatial resolution of the data (see Results). For each bird, we used a calibration period spanning from the day after it was banded through 1 August 2015 (median = 57 days, 44–80 days); during this time period, we assumed the bird was present on its breeding territory. We compared movement patterns of grassland birds between sites in the Midwest (Kansas, North Dakota, Minnesota, and Wisconsin) and the East Coast (Maryland and Massachusetts). Created in 1903 by President Theodore Roosevelt, today's National Wildlife Refuge System protects habitats and wildlife across the country, from the Alaskan tundra to subtropical wetlands. Version 3.5.1, A hidden Markov model for reconstructing animal paths from solar geolocation loggers using templates for light intensity, Phenological matching across hemispheres in a long‐distance migratory bird, Integrating concepts and technologies to advance the study of bird migration, Dynamic distributions and population declines of Golden‐winged Warblers, Golden‐winged Warbler ecology, conservation, and habitat management, From birds to butterflies: Animal movement patterns and stable isotopes, The evolutionary significance of bird migration, Field‐testing a new miniaturized GPS‐Argos satellite transmitter (3.5 g) on migratory shorebirds, Flexible reaction norms to environmental variables along the migration route and the significance of stopover duration for total speed of migration in a songbird migrant, Optimal conservation planning for migratory animals: Integrating demographic information across seasons, Winter habitat quality, population limitation, and conservation of Neotropical‐Nearctic migrant birds, Intraspecific variation in migratory pattern of a partial migrant, the Blue Tit (, Repeat tracking of individual songbirds reveals consistent migration timing but flexibility in route, Predicting the consequences of habitat loss for migratory populations, Effects of grazing on vegetation structure, prey availability, and reproductive success of Grasshopper Sparrows, Migratory connectivity and population‐specific migration routes in a long‐distance migratory bird, Grasshopper sparrow (Ammodramus savannarum), version 2.0, Climate change leads to decreasing bird migration distances, The importance of understanding migratory connectivity and seasonal interactions, Birds of two worlds: The ecology and evolution of migration, Links between worlds: Unraveling migratory connectivity, Differential migration and the link between winter latitude, timing of migration, and breeding in a songbird, Rapid and continued population decline in the Spoon‐billed Sandpiper. Grasshopper Sparrows from Midwest populations wintered in Mexico (n = 10), Texas (n = 2), or the Florida panhandle (n = 1), whereas East Coast sparrows (n = 20) wintered in Florida, the Greater Antilles, or possibly the Bahamas (Figures 4 and the course of a month, typic5; See Supporting Information Figure S1). Sparrows fitted with a geolocator received a unique combination of leg bands: three colored plastic and one USGS aluminum. Learn more. For both species, an extended inter‐state or international collaborative approach is likely needed to identify and manipulate habitat conditions that improve individual condition and increase survival during the nonbreeding season. At the time of recapture, most geolocator harnesses fit loosely with ~1 cm of vertical play when the geolocator was lifted vertically from the birds' backs. As assessed via aerial photography, Eastern Meadowlarks predominantly used agricultural grasslands (e.g., hayfields) throughout their migration and nonbreeding periods (Hill & Renfrew, 2018b). We thank all of the biological field technicians and crew leaders and the biologists and staff of the Fire Desks, Air Traffic Control Towers, and Range Controls that supported our research and kept us safe at Fort Riley (KS), Camp Grafton (ND), Fort McCoy (WI), Camp Ripley (MN), Joint Base Cape Cod (MA), Westover Air Reserve Base (MA), and Naval Air Station Patuxent River (MD). (2012) used geolocators to monitor the migration of 13 Snow Buntings (Plectrophenax nivalis) from Nunavut, Canada, in two consecutive years. Here, we examine the movement ecology of Grasshopper Sparrows (Ammodramus savannarum) and Eastern Meadowlarks (Sturnella magna); two species that breed across much of the Midwest and eastern United States have undergone steep declines (≥2.5% per year, 1966–2015; Sauer et al., 2017), but are locally common. Grasshopper Sparrows migrate nocturnally, likely within small groups of conspecifics or as individuals, and are difficult to detect outside of the breeding season when on the ground and not singing (Evans & Mellinger, 1999; Vickery, 1996). We recaptured all but one color‐banded sparrow that we relocated in 2016, and all recaptured birds were still wearing their geolocators. Our approach explicitly incorporates nonbreeding location uncertainty in the estimation of the UD; see (Hill & Renfrew, 2001) for FLightR‐related R code complete with tutorial. To avoid similar model behavior, we followed the approach of Cooper et al. Multiple factors including competition for resources or mates and predation risk have been linked to partial migration, but the decision to stay or migrate is largely dependent on individual condition (Chapman, Brönmark, Nilsson, & Hansson, 2011). When they removed information about migratory connectivity from the model, the optimal strategy to bolster the species overall unintentionally resulted in the near‐extinction of some regional populations. Number of times cited according to CrossRef: The Importance of Isotopic Turnover for Understanding Key Aspects of Animal Ecology and Nutrition. We recaptured male sparrows with mist nets deployed within flight lanes and used audio playback when netting alone was unsuccessful.